Design your configuration plan

Start small and grow gradually as you design the CMDB with
configuration items.

Take the time to familiarize yourself with the CMDB and its features
and functions. Develop an understanding of design options for the CMDB
and the broader ecosystem of federated systems and data feeds.

Your CMDB is populated with configuration items (CIs), which must be
classified for you to have a properly managed CMDB. When you start
this process, start small and grow gradually. Also make sure that
there are no duplicate CIs.

What is a CI? A CI is one of the most important components of your CMDB. It’s
simply an application, infrastructure, or service component you’re
managing. It can be a physical server, an app running on a virtual
server, or a business service.

Decide which CI classes and attributes you need to support the use
cases you identified in Stage 1. Most organizations start simple
and make incremental improvements as they gain experience. From this,
you should be able to identify the types of CI classes you will need
to manage. You will need to make sure these CI classes are at the
appropriate level—as in what level of definition is meaningful to the
use cases you identified earlier. As a general recommendation, start
with using the CI classes defined out‑of‑the‑box for CIs that can be
discovered with ServiceNow. These CI classes have been vetted by
thousands of our customers and should contain all the attributes your
efforts will need.

For example, you might start with a hardware CI class, so you assign
some simple attributes: CPU, memory, etc. As you build your CMDB,
you’ll map computers, servers, routers, switches, and so on. Each of
these CIs will have attributes and each one of them will have
relationships and dependencies.

Heads up! Your CI tables can get out of control quickly if you don’t
simplify them! Keep their names intuitive so they are easy to identify
and remember. One large insurance customer warns that it’s easy to add
data to the CMDB but harder to maintain the model.

Figure 1: Example of a table extension model that grows with complexity

Our customers start by classifying these CIs:

Windows server

Linux server

Firewall

Load balancer

Database

Network Router

Network Switch

Storage

Application Server

For CI classes that are not discoverable, you might need to extend an
out‑of‑the‑box class. Figure 1 depicts how the CMDB uses
object‑oriented inheritance in the creation of all CI classes.

If you are using ServiceNow Discovery, it will find all the network
infrastructure, applications, and services and populate them into the
CMDB. Dependency maps let you see where your CIs support a critical service.

For example, the loss of disk drives may take a database instance
down, which affects the requisition service the HR department uses to
order equipment for new employees. If you are using ServiceNow
Discovery or Service Mapping products, the dependencies between
discoverable CIs will be built for you automatically as the CMDB is
updated by discovery updates. See Figure 2.

Figure 2: ServiceNow CMDB dependency map

For the logical “business layers” that are not discoverable, you need
to define the relationships between discoverable and nondiscoverable
CIs in your business model.

For each CI class, you will need to make sure the CMDB is configured
properly. Use CI Class Manager to configure the rules for each CI
class to ensure you have all the necessary information about your CIs
in one place. The CMDB stores all the information you want to capture
and manage on an ongoing basis and can record relationships between
attributes in the CMDB.

Figure 3: ServiceNow CI Class Manager

In order to manage changes to CMDB, we recommend setting up
Configuration Control that eliminates risks of unnecessary tweaks to
the CIs. Based on customer implementations, we suggest that you
proactively manage CIs and their dependencies when they’re added,
deleted, and modified. When a business process like incident
management requests a change to the CIs, you should:

Allow change requests via Change Management. You can easily do
this using the Propose Change feature if you have ServiceNow
Change Management enabled.

Assign proper privileges to the
authorized users to make changes; normally it’s a member of your
team such as a CM analyst.

Update the CMDB with the necessary changes and communicate to
stakeholders.

EXPERT TIP

Start with populating your CMDB with a solid inventory of CIs focused
on specific use cases. If you find yourself populating with items that
do not tie back to your goal or use case, you are off track.